空气中微小固体单球非稳动力学特性实验研究
发布时间：2018-09-07 16:44
【摘要】：工程应用和环境治理领域中经常涉及到纳米至微米级的固体单颗粒在气体中运动的动力学问题。但是至今为止,对于气体中微小固体颗粒在非稳态(加速度不为零)运动中的动力学特性的研究甚少。为此,本文实验研究了粒径为0.1mm-0.5mm的单体固体微球在气体中的非稳态运动的动力学行为。本文首先设计微小球形颗粒风洞实验装置,利用该装置结合本文提出的一种实验方法,可将固体微球在气流中的非稳态运动过程展示在一枚镜头下。得到该颗粒在静止空气中从开始由静止状态一直运动到匀速状态的完整下落过程,得到整个过程的颗粒位移-时间和速度-时间关系的实验数据；通过对实验数据整理得出经验函数CD=f(Re),并带入颗粒的控制方程,求得解析解。即：颗粒的位移-时间和速度-时间理论计算公式。研究发现,在非稳态过程中,该方法所得的颗粒位移和速度曲线的平均相对误差仅为1.69%和2.22%,其精度成倍优于前人的处理方法,并且规避了Re和CD的盲目估值,反复试算过程。然后,利用该实验装置,在风速0～11m/s范围内,分别对0.1-0.5mm玻璃珠、0.2-0.5mm焊锡珠进行非稳态测试实验(Re范围为4.47-368.89);对非稳态运动过程中颗粒的附加质量力和Basset力与粘性阻力的比值进行计算；对CD-Re实验数据进行曲线拟合。研究发现,微小球体的附加质量力和Basset力与粘性阻力的比值分别为0.25%和2.2%,因此附加质量力和Basset力可忽略不计,并且实验结果与前人经验模型保持一致。最后,对微小球形颗粒在圆弧形弯道流场中非稳态运动进行了实验研究；对圆弧形旋流流道内部流场进行CFD数值仿真,并采用准自由涡理论对圆弧形旋流流道内部流场进行数学建模；将0.2mm、0.35mm和0.5mm颗粒分别在10m/s、13m/s和16m/s入口风速的旋流场中进行非稳态运动实验,得到其径向和切向方向上的位移、速度和加速度数据；建立颗粒在自由涡旋流场中运动的数学模型,用数值求解法,将实验结果与所得理论曲线进行对比。研究发现,理论计算存在一定程度的误差,对于颗粒位移和速度,实测值比计算值偏大,弯道流场中的二次流对颗粒径向方向的运动影响非常小,可以忽略。本课题属于基础实验性研究,将单个固体小球非稳态运动实验所用球体的直径由前人所做实验的0.29mm降低到0.1mm,并且对微小球体从静止开始运动直到稳定的过程进行实验观测和理论建模。所得的实验数据和经验公式对新型除尘器的研发,甚至微小颗粒气固两相流动有一定的参考价值。
[Abstract]:In the field of engineering applications and environmental control, the dynamics of the movement of nanometer-to-micron solid single particles in gas is often involved. However, so far, little research has been done on the dynamic characteristics of small solid particles in unsteady motion (acceleration is not zero). Therefore, the dynamic behavior of the unsteady motion of monomeric solid microspheres with particle size of 0.1mm-0.5mm in gas has been studied experimentally in this paper. In this paper, a wind tunnel experimental device for micro spherical particles is designed. The unsteady motion process of solid microspheres in airflow can be displayed under a lens by using this device combined with an experimental method proposed in this paper. The complete falling process from static state to uniform state in the stationary air is obtained, and the experimental data of the displacement-time and velocity-time relations of the whole process are obtained. Based on the experimental data, the empirical function CD=f (Re), is obtained and the governing equation brought into the particle is obtained, and the analytical solution is obtained. Namely: displacement-time and velocity-time theory of particle calculation formula. It is found that the average relative errors of the particle displacement and velocity curves obtained by this method are only 1.69% and 2.22% in the unsteady state process, and the accuracy of the proposed method is several times better than that of the previous methods, and the blind estimation of Re and CD is avoided and the process of repeated trial calculation is avoided. Then, using the experimental device, within the range of wind speed 0~11m/s, The unsteady test of 0.1-0.5mm glass bead 0.2-0.5mm solder bead (Re range 4.47-368.89), the calculation of the additional mass force of particles and the ratio of Basset force to viscous resistance during unsteady motion, and the curve fitting of CD-Re experimental data were carried out. It is found that the additional mass force and the ratio of Basset force to viscous resistance are 0.25% and 2.2%, respectively, so the additional mass force and Basset force can be ignored, and the experimental results are consistent with the previous empirical model. Finally, the unsteady flow field of small spherical particles in a circular curved channel is experimentally studied, and the CFD numerical simulation of the flow field in a circular arc swirl channel is carried out. Using quasi-free vortex theory, the internal flow field of circular arc swirl channel is modeled, and the unsteady motion experiments of 0.2mm ~ 0.35mm and 0.5mm particles are carried out in the swirl flow field of 10 m / s ~ (13) m / s and 16m/s inlet wind speed respectively, and the displacement in radial and tangential direction is obtained. The velocity and acceleration data and the mathematical model of particle motion in the free vortex flow field are established. The experimental results are compared with the theoretical curves obtained by the numerical solution method. It is found that there is a certain degree of error in the theoretical calculation. For the displacement and velocity of particles, the measured value is larger than the calculated value, and the secondary flow in the bend flow field has little effect on the radial movement of the particle, which can be ignored. This subject belongs to the basic experimental research. The diameter of the sphere used in the unsteady motion experiment of a single solid sphere was reduced from the 0.29mm of the previous experiment to 0.1 mm, and the experimental observation and theoretical modeling of the process of the small sphere moving from rest to stability were carried out. The experimental data and empirical formulas are valuable for the research and development of new type dust catcher and even for the gas-solid two-phase flow of tiny particles.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ021;TQ050.2
本文编号：2228830
[Abstract]:In the field of engineering applications and environmental control, the dynamics of the movement of nanometer-to-micron solid single particles in gas is often involved. However, so far, little research has been done on the dynamic characteristics of small solid particles in unsteady motion (acceleration is not zero). Therefore, the dynamic behavior of the unsteady motion of monomeric solid microspheres with particle size of 0.1mm-0.5mm in gas has been studied experimentally in this paper. In this paper, a wind tunnel experimental device for micro spherical particles is designed. The unsteady motion process of solid microspheres in airflow can be displayed under a lens by using this device combined with an experimental method proposed in this paper. The complete falling process from static state to uniform state in the stationary air is obtained, and the experimental data of the displacement-time and velocity-time relations of the whole process are obtained. Based on the experimental data, the empirical function CD=f (Re), is obtained and the governing equation brought into the particle is obtained, and the analytical solution is obtained. Namely: displacement-time and velocity-time theory of particle calculation formula. It is found that the average relative errors of the particle displacement and velocity curves obtained by this method are only 1.69% and 2.22% in the unsteady state process, and the accuracy of the proposed method is several times better than that of the previous methods, and the blind estimation of Re and CD is avoided and the process of repeated trial calculation is avoided. Then, using the experimental device, within the range of wind speed 0~11m/s, The unsteady test of 0.1-0.5mm glass bead 0.2-0.5mm solder bead (Re range 4.47-368.89), the calculation of the additional mass force of particles and the ratio of Basset force to viscous resistance during unsteady motion, and the curve fitting of CD-Re experimental data were carried out. It is found that the additional mass force and the ratio of Basset force to viscous resistance are 0.25% and 2.2%, respectively, so the additional mass force and Basset force can be ignored, and the experimental results are consistent with the previous empirical model. Finally, the unsteady flow field of small spherical particles in a circular curved channel is experimentally studied, and the CFD numerical simulation of the flow field in a circular arc swirl channel is carried out. Using quasi-free vortex theory, the internal flow field of circular arc swirl channel is modeled, and the unsteady motion experiments of 0.2mm ~ 0.35mm and 0.5mm particles are carried out in the swirl flow field of 10 m / s ~ (13) m / s and 16m/s inlet wind speed respectively, and the displacement in radial and tangential direction is obtained. The velocity and acceleration data and the mathematical model of particle motion in the free vortex flow field are established. The experimental results are compared with the theoretical curves obtained by the numerical solution method. It is found that there is a certain degree of error in the theoretical calculation. For the displacement and velocity of particles, the measured value is larger than the calculated value, and the secondary flow in the bend flow field has little effect on the radial movement of the particle, which can be ignored. This subject belongs to the basic experimental research. The diameter of the sphere used in the unsteady motion experiment of a single solid sphere was reduced from the 0.29mm of the previous experiment to 0.1 mm, and the experimental observation and theoretical modeling of the process of the small sphere moving from rest to stability were carried out. The experimental data and empirical formulas are valuable for the research and development of new type dust catcher and even for the gas-solid two-phase flow of tiny particles.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ021;TQ050.2
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